Purification of battery acid



Feb. 21, 1933.' c c ROSE 1,898,688

PURIFICATION OF BATTERY ACID Filed Sept. 16, 1951 STEAM ACT VA TED CAR80 N i FILTRATE ,Erz verz for" f m MMT7 Patented Feb. 21, 1933 UNITEDSTATES PATENT OFFICE CLARENCE G. ROSE, OF CLEVELAND, OHIO, ASSIGNOR TOWILLARD STORAGE BATTERY COMPANY, OF CLEVELAND, OHIO, A CORPORATION OFWEST VIRGINIA PURIFICATION OF BATTERY ACID Application filed September16, 1931.

This invention relates to the purification of battery acid. It has to doprimarily with the treatment of sulphuric acid employed in batteriesduring the original charging of the batteries, or the forming of theplates thereof. The electrolyte thus used is generally of lower specificgravity than that normally employed in a fully charged battery. Hence,after it has performed its function, it is dumped from the battery andnew acid of higher specific gravity is introduced in its place.

If wood separators are employed in the battery, this dumped acid iscontaminated more or less by wood acids, principally acetic acid,present to a small degree in the wood separators. Such impure acidcannot be economically used a second time for the reason that the woodacids therein subject the positive plates of the battery to scaling andgrid corrosion. This action is very noticeable when acid containing morethan .01% wood acid is used for the initial formation of a battery. Theamount of wood acids which the dumped electrolyte is likely to containwill depend upon the thoroughness with which the wood separators havebeen treated before they are used. In almost every case, however, thewood acid content of this electrolyte is found to be more than .01% andis genqe rally in the neighborhood of .03% or .04 0. dumped electrolytea second time without dis astrons results.

Prior to the present invention, the only method known for removing thesewood acids from the battery acid involved boiling the impure acid downto a high acid concentration and then aerating it with compressed air,which is an expensive and troublesome process. After considerableexperimentation, I have discovered that the removal of the wood acidsmay be effected directly, that V is, without boiling down, by the simpleex- Hence it is impossible to use such Serial No. 563,036.

means which I prefer to employ is that illustrated more or lessdiagrammatically in the accompanying drawing, the single figure of whichis an elevational view of the apparatus,

with some parts broken away to more clearly illustrate the invention.

In the drawing, 10 represents a relatively long tubular container ofacid resisting material, into the bottom of which opens a pipe 11 forthe admission of the impure acid, a valve 12 being employed for shuttingoff and controlling the rate of flow of the acid, it being understoodthat the acid is to be fed through the apparatus under pressureengendered by a pump or gravity resulting from the elevation of the acidtank with respect to the apparatus in question. A second pipe 13 alsomakes connection with the lower end of container 10, this pipe having ashut-oil valve 14, and being employed for carrying off the impuritiesabsorbed by the carbon.

Just above the bottom of the container 10 there is mounted a grid 15upon which is supported a small quantity of coke 16 that is employed forholding the finer activated carbon .17. enclosed by the tubularcontainer. The

height and diameter of the container 10 are dependent upon the rate offiow of the acid therethrough, it being necessary to maintain the acidin contact with the carbon for a given length of time.

Near the upper end of container 10 I mount a second grid 18 to preventthe carbon from being carried oil with the outgoing acid. Just abovethis grid there is a draw-off pipe 19 in which is mounted a valve 20. Atthe top of the container 10 there is a connection to a steam pipe 21.

- lVhen the process is to be started, the Valve 14 is closed and thevalves 12 and 20 are opened, the valve 12 being opened partway only, ifdesired, so as to control the rate of flow of the acid into thecontainer 10. The coke 16, in addition to supporting the finer carbon17, acts as a filter to remove any solid material which may have gotteninto the battery acid. The latter then flows gradually upward throughthe activated carbon 17 and the wood acid is absorbed thereby, thefiltrate which passes off through the grid 18 and pipe 19 being pure, orsubstantially pure, sulphuric acid capable of being used again in theformation of new batteries. In fact the acid may be used indefinitelywhen it is purified by my method after each forming operation.

When the activated carbon has become saturated or so much so that thedischarge is no longer of satisfactory purity, the percolation isstopped by the closing of valve 12. Valve 14 is then opened and the acidin the container permitted to drain ofi'. Then the valve 20 is closedand steam is introduced through pipe 21 and forced through the activatedcarbon and out through waste pipe 13. The carbon is thereby heated andthe acid previously absorbed is driven off as a vapor, it being carriedout through the waste pipe with the exhaust steam. When this cleaningoperation has been continued a suliicient length of time, determined bytest, the steam is turned off, the valve 14 closed, and the valves 12and 20 opened for the resumption of the acid purifying process.

In the foregoing description, I have necessarily gone somewhat intodetail in order to explain fully the particular embodiments of theinvention herein illustrated, but I desire it to be understood that suchdetail disclosure is not to be construed as amounting to a limitation,except as it may be included in the appended claims.

Having thus described my invention, I claim:

1. The method of separating wood acid impurities from sulphuric acid,which consists in bringing the impure acid into contact with activatedcarbon.

2. The method of separating acetic acid impurities from sulphuric acid,which consists in bringing the impure acid into contact with activatedcarbon.

3. The method of reclaiming sulphuric acid from battery acid adulteratedwith wood acids, which consists in bringing the impure acid into contactwith activated carbon, and maintaining the contact a sufiicient lengthof time for the removal of the wood acids by the carbon.

at. The method of removing wood acid impurities from sulphuric acid,which consists in passing the impure acid through activated carbon.

5. The method of removing wood acid impurities from sulphuric acidemployed in bat-- tery formation, which consists in passing the impureacid upwardly through a column'of activated carbon.

6. The method of removing wood acid impurities from sulphuric acidemployed in battery formation, which consists in passing the impure acidupwardly through a column of granular activated carbon.

7. The method of removing wood acid impurities from sulphuric acidemployed in battery formation, which consists in bringing signature.

CLARENCE C. ROSE.

